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How to start a Public Cloud instance on a bootable volume

Stephanie R.
Updated

Learn how to start an instance on an attached volume.

Public Cloud instances come with an original disk that is copied from a system image (Debian 12, Windows Server, etc.). It is also possible to use additional volumes, which are persistent disks that will allow data to be stored.

You can also deploy an operating system to and from a volume. The Public Cloud instance will then start on this volume instead of the original disk.

diagram_compareClassicBoot_bootFromVolume.png

OpenStack natively allows you to boot from a volume. It involves making the volume bootable and starting the instance from this volume. The changes will cause the original disk to be replaced by the new volume. The functionality described in this guide eliminates the need to access the original disk and, therefore, takes advantage of the volume.

NOTE: With the current version of OpenStack, rescue-pro mode is not available on an instance booted via a bootable volume.

 

Requirements

 

Instructions

Creating a bootable volume from an image

Log in to the Horizon interface.

Select the appropriate region from the drop-down menu at the top left.

On the Project tab, open the Volumes section and click the Volumes dashboard.

Click on Create Volume.

horizon_volumes_dashboard.png

In the dialog box that opens, enter or select the following values:

  • Volume Name
  • Description (optional)
  • Volume Source: Image
  • Use image as a source
  • Type
  • Size (GB)
  • Availability Zone: nova

Click on Create Volume.

horizon_createVolume_configurator.png

The volume will be in a creating state then a downloading state before being available.

If you click the volume name, you will see the volume's details and that the Bootable line says Yes.

horizon_volumeDetails.png

You can create a bootable volume from an existing image, volume, or volume snapshot. This procedure shows you how to create a volume from an image and use the volume to boot an instance.

$ openstack image list

Note the ID or the name of the image that you wish to use.

Create a bootable 10GB high-speed volume named volume_ubuntu from an Ubuntu 24.04 image:

You can install an image on a volume using the --image argument:

$ openstack volume create --type high-speed --image 2c2e28dc-9124-49c3-b92d-7f00bd83ac86 --size 10 volume_ubuntu
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| attachments         | []                                   |
| availability_zone   | nova                                 |
| bootable            | false                                |
| consistencygroup_id | None                                 |
| created_at          | 2025-02-06T17:04:34.000000           |
| description         | None                                 |
| encrypted           | False                                |
| id                  | d7611318-fd7b-4b6a-8a7a-8d368049f747 |
| multiattach         | False                                |
| name                | volume_ubuntu                        |
| properties          |                                      |
| replication_status  | None                                 |
| size                | 20                                   |
| snapshot_id         | None                                 |
| source_volid        | None                                 |
| status              | creating                             |
| type                | high-speed                           |
| updated_at          | None                                 |
| user_id             | 1a67934f87ef481d9cb617a913bfa8bb     |
+---------------------+--------------------------------------+

In this command, 2c2e28dc-9124-49c3-b92d-7f00bd83ac86 is the Ubuntu 24.04 image ID.

Cinder makes a volume bootable when the --image parameter is passed.

 

Starting an instance using a bootable volume

Log in to the Horizon interface.

Select the appropriate region from the drop-down menu at the top left.

On the Project tab, open the Compute section and choose Instances.

Click on Launch Instance.

horizon_instances_dashboard.png

In the Launch Instance dialog box, enter the information requested. Refer to the guide Create an instance from the Horizon interface for more details.

In the Source tab, choose Volume in the Select Boot Source field.

A new field for volume selection appears. You can select the previously created volume from the list.

Make your selections in the Details, Flavor, and Networks areas. Click on Launch Instance.

horizon_createInstance_configurator.png

The instance will be in a build state then Block Device Mapping state before being available.

The instance will eventually have the volume attached.

horizon_instanceDetails.png

Create an instance, specifying the bootable volume volume_ubuntu as the boot device.

openstack server create --volume volume_ubuntu --flavor d2-2 --key-name publickey --nic net-id=Ext-Net InstanceTest

List the volumes to ensure the status has changed to in-use and the volume is correctly reporting the attachment:

$ openstack volume list
+--------------------------------------+---------------+--------+------+--------------------------------------+
| ID                                   | Name          | Status | Size | Attached to                          |
+--------------------------------------+---------------+--------+------+--------------------------------------+
| d7611318-fd7b-4b6a-8a7a-8d368049f747 | volume_ubuntu | in-use | 10   | Attached to InstanceTest on /dev/sda |
+--------------------------------------+---------------+--------+------+--------------------------------------+

List the volumes attached to the InstanceTest Instance:

$ openstack server volume list InstanceTest
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+
| ID                                   | Device   | Server ID                            | Volume ID                            | Tag  |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+
| d7611318-fd7b-4b6a-8a7a-8d368049f747 | /dev/sda | 5d97c190-f2e3-4af4-a010-6fa7bffbf88b | d7611318-fd7b-4b6a-8a7a-8d368049f747 | None |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+

You can also create an instance, using the chosen image and requesting "boot from volume" behavior.

$ openstack server create --flavor d2-2 --key-name publickey --nic net-id=Ext-Net --image b680f0aa-8eb8-4ac8-b008-2a90bb71af4f --boot-from-volume 10 InstanceTest2
+-----------------------------+---------------------------------------------+
| Field                       | Value                                       |
+-----------------------------+---------------------------------------------+
| OS-DCF:diskConfig           | MANUAL                                      |
| OS-EXT-AZ:availability_zone |                                             |
| OS-EXT-STS:power_state      | NOSTATE                                     |
| OS-EXT-STS:task_state       | scheduling                                  |
| OS-EXT-STS:vm_state         | building                                    |
| OS-SRV-USG:launched_at      | None                                        |
| OS-SRV-USG:terminated_at    | None                                        |
| accessIPv4                  |                                             |
| accessIPv6                  |                                             |
| addresses                   |                                             |
| adminPass                   | dP4e4iY3eWWC                                |
| config_drive                |                                             |
| created                     | 2025-02-06T17:20:06Z                        |
| flavor                      | d2-2 (dc3fe9e7-e374-4ad8-b200-fa3bdf45069f) |
| hostId                      |                                             |
| id                          | a4632249-e1b4-4047-be1c-87f8b0328f7c        |
| image                       | N/A (booted from volume)                    |
| key_name                    | publickey                                   |
| name                        | InstanceTest2                               |
| progress                    | 0                                           |
| project_id                  | d7fb756ae2c24b1cb8630ec7f56ee4a8            |
| properties                  |                                             |
| security_groups             | name='default'                              |
| status                      | BUILD                                       |
| updated                     | 2025-02-06T17:20:06Z                        |
| user_id                     | 1a67934f87ef481d9cb617a913bfa8bb            |
| volumes_attached            |                                             |
+-----------------------------+---------------------------------------------+

In the command above, b680f0aa-8eb8-4ac8-b008-2a90bb71af4f is the Debian 12 image ID.

  • List the volumes:

List the volumes to ensure the status has changed to in-use and the volume is correctly reporting the attachment.

$ openstack volume list
+--------------------------------------+---------------+--------+------+----------------------------------------+
| ID                                   | Name          | Status | Size | Attached to                            |
+--------------------------------------+---------------+--------+------+----------------------------------------+
| 27f8332d-8bfd-4515-b0a8-18667ae50ff8 |               | in-use | 10   | Attached to InstanceTest2 on /dev/sda  |
| d7611318-fd7b-4b6a-8a7a-8d368049f747 | volume_ubuntu | in-use | 10   | Attached to InstanceTest on /dev/sda   |
+--------------------------------------+---------------+--------+------+----------------------------------------+

List the volume on the server to make sure it's properly attached.

$ openstack server volume list InstanceTest2
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+
| ID                                   | Device   | Server ID                            | Volume ID                            | Tag  |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+
| d7611318-fd7b-4b6a-8a7a-8d368049f747 | /dev/sda | 5d97c190-f2e3-4af4-a010-6fa7bffbf88b | d7611318-fd7b-4b6a-8a7a-8d368049f747 | None |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+------+

 

Go further

For more information and tutorials, please see our other Public Cloud support guides or explore the guides for other OVHcloud products and services.

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